1. Field of the Invention
The present invention pertains to novel enaminoketones containing a CF3O-group, novel pyrazole-derivatives containing a CF3O group as well as to a novel process for their preparation comprising aminoformylation of CF3O-ketones and cyclization of the obtained CF3O-enaminoketones with hydrazines to trifluoromethoxy pyrazoles.
2. Description of Related Art
Fluorine as a substituent in active ingredients plays a significant and increasingly important role. The biggest group of fluorinated pesticides are the compounds containing a trifluoromethyl group (mainly in aromatic rings), followed by aromatic compounds containing at least one isolated fluorine atom. Only five pesticides contain OCF3-groups are on the market. It was estimated that the number of fluorinated compounds currently under development represent some 35-50% of all the active ingredients under development as described in The pesticide manual, XIII edition; British crop protection council, 2003.
For the preparation of trifluoromethoxy substituted arenes the chlorination of aromatic methyl groups and exchange with fluorine can be used as disclosed in Yagupol'skii, L. M. Dokl. Akad. Nauk SSSR.
When aryl formates are treated with sulfur tetrafluoride, (trifluoromethoxy)arenes are obtained in yields ranging from 9-81% as described in Sheppard, W. A. J. Org. Chem. 1964, 29, 1-11.
The oxidative fluorodesulfurization fluorination allows the conversion of dithiocarbonates (xanthogenates) with a huge excess of hydrogen fluoride-pyridine and 1,3-dibromo-5,5-dimethylhydantoin into (trifluoromethoxy)arenes in moderate to excellent yields as disclosed in Kuroboshi, M.; Suzuki, K.; Hiyama, T. Tetrahedron Lett. 1992, 33, 4173-4176; Kanie, K.; Tanaka, Y.; Suzuki, K.; Kuroboshi, M.; Hiyama, T. Bull. Chem. Soc. Japan 2000, 73, 471-484; Kuroboshi, M.; Kanie, K.; Hiyama, T. Adv. Synth. Catal. 2001, 343, 235-250 and Shimizu, M.; Hiyama, T. Angew. Chem. Int. Ed. 2005, 44, 214-231.
Obviously, the best synthesis of trifluoromethyl ethers would be the direct introduction of the whole OCF3 moiety. This was first done by radical condensation of olefins and trifluoromethyl hypofluorite (Rozen, S. Chem. Rev. 1996, 96, 1717-1736) which is highly hazardous and toxic. Then, numerous attempts to carry out nucleophilic trifluoromethoxylation with trifluoromethoxide salts failed since, generally, CF3O— anion collapses into fluoride and fluorophosgene, even at low temperature.
DE 10 2007 036702 A1 pertains to synergistic herbicidal combinations comprising an herbicide from the group of pyrazolylphenyl derivatives optionally containing a CF3O-group as a substituent. DE 102006 050516 A1 pertains to Dihydropyrazolon-derivatives optionally containing a CF3O-group and processes for their synthesis for use as drugs. Both documents do not contain information about the methods of the preparation of CF3O-derivatives nor do they disclose references indicating how such a CF3O-group can be introduced into the pyrazol moiety or its pre-cursors.
There is presently no generally applicable procedure that allows the preparation of trifluormethoxypyrazoles. Due to the importance of heterocyclic structures in agrochemical ingredients and the use of fluorine atoms and fluorinated groups in general, the possibility to prepare OCF3-heterocycles will lead to new, so far unknown ingredients.
There is thus a strong need for a generally applicable process for the preparation of —OCF3 pyazoles.